The present invention relates in general to a device for altering the degree of moisture in a designated storage space, and more particularly, to a humidity altering device for maintaining a specific humidity level in a humidor designed for the storage of humidity sensitive products.
A number of perishable commodities such as food products and tobacco products retain their optimum freshness and desirable properties when stored in environments in which a predetermined relative humidity is maintained. In addition, other products such as fabrics, rare books, drawings, paintings and the like require storage at specific relative humidity levels to reduce degradation and to prevent cracking and warpage.
The relative humidity in an enclosed generally airtight package can be controlled by providing a humectant, such as a water-based solution, within the package maintained in its liquid phase. The humectant liquid vaporizes in the package thereby producing water vapor. When the partial pressure of the water vapor is equal to the vapor pressure of the water for the humectant solution, an equilibrium is reached where the humectant gives off water vapor at the same rate as water vapor condenses back into the humectant liquid. Depending upon the equilibrium vapor pressure of the water over the humectant solution selected, a predetermined relative humidity may be established in the enclosed package.
It can be appreciated that it is important that the humectant solution be isolated from direct contact with the product being stored in the humidified environment. In this regard, there is known from Durocher, U.S. Pat. No. 4,997,082, a package having controlled humidity for storing humidity sensitive products such as tobacco and food products. The package is constructed as an enclosed container which stores a humidistat pad serving as a spacer, while also holding a humectant solution in its liquid phase in an absorbent interior layer. The pad is provided with a liquid impervious backing layer to protect the walls of the container from the liquid humectant solution. The pad also includes a liquid permeable cover which can rapidly transfer the humectant solution to the absorbent layer during filling of the package with the product to be stored. Also known was the use of a block of highly acetylized polyvinyl alcohol sponge material placed into a plastic bag having holes on opposing ends of the bag. The bag was confined within a housing having open ends opposing the holes in the bag. The bag was held in place within the housing using stainless steel screen material that was swedged into the open ends of the housing. Other known humidity altering devices are known from Morgan, U.S. Pat. No. 3,924,807 and Guehler et al., U.S. Pat. No. 3,801,011.
While the prior art discloses a number of humidity altering devices, there is the need for improvements in such devices so as to enable maintaining a specific humidity level in a humidor designed for the storage of humidity sensitive products.